Advisory Visit River Lagan, Dromore, Co. Down July 2011 1.0 Introduction This report is the output of a site visit undertaken by Tim Jacklin and Paul Gaskell of the Wild Trout Trust to the River Lagan, Co. Down, Northern Ireland on 30th June, 2011. Comments in this report are based on observations on the day of the site visit and discussions with Michael Shanks and Donald McClearn of Dromore and District Angling Club (DADAC) and subsequent discussion with Dr. Robert Rosell of the Agri-Food and Biosciences Institute (AFBI). Normal convention is applied throughout the report with respect to bank identification, i.e. the banks are designated left hand bank (LHB) or right hand bank (RHB) whilst looking downstream. 2.0 Catchment / Fishery Overview The source of the Lagan is on Slieve Croob, the tallest of a group of peaks in central County Down, between Dromara and Castlewellan. The river’s course takes it from Slieve Croob , through Dromara, Dromore, Lisburn and Belfast where it enters Belfast Lough, an inlet of the Irish Sea. The river’s salmon population became extinct in the early C19th and a restoration project for the species has been carried out over the last 30 years (Robert Rosell, pers. comm.). Dromore and District Angling Club control the angling on the river in the vicinity of the town of Dromore and look after the upper reaches and tributaries of the river where trout and occasionally salmon spawn. DADAC is a trout angling club and has around 80 – 100 members. The club employs the services of a hatchery to catch up trout broodstock in the upper river and stock fed fry back into the river. Salmon fry are also stocked into the river and tributaries as part of the restoration scheme. Trout stocks within the DADAC waters on the Lagan are reported to be good and reasonable numbers were seen rising (and caught during an evening’s angling). The club is however concerned about other changes observed within the river, namely a large reduction in the amount of water crowfoot (Ranunculus sp.) and reduced fly hatches. In addition, the formerly clean river bed is now regularly covered with a veneer of very fine sediment. 3.0 Habitat Assessment The upper reaches of the river were inspected briefly from the road bridge (Grid Reference NW 39314 02822). The river here was very open with overgrazed banks and little cover from riparian vegetation. Fencing and /or a reduction in grazing pressure is needed to improve the riparian zone. Some fencing had recently been completed just upstream of the road bridge (Photos 1, 2). At the next road bridge downstream (NW 38703 03794) there was a recently constructed fish pass just downstream of the bridge culvert. The pass was constructed to improve fish access across a known obstruction and also included works to shore up the left bank downstream of the bridge which was becoming undermined, threatening a property. The works were part- funded by DADAC and carried out by the Rivers Agency with design input by Robert Rosell (pers. comm.). The pass is a baffled, Denil-type and the downstream water levels have been raised by the installation of a rock weir (Photo 3). Upstream of the Denil pass there remain some challenges for fish passage and some opportunities for improvement. At the time of the visit (low flow) there was a lip at the upstream end of the Denil (Photo 4) which is not ideal; this will be drowned out at higher flows but removing it would increase the window of opportunity for fish migration. Upstream of this point, mass concrete studded with rocks was present, up to the base of the bridge culvert; a low-flow channel was present within the mass concrete, but it was quite shallow and a lip was present at the downstream end, again limiting the range of flows when fish passage is possible (Photos 4, 5). The bridge culvert (Photo 5) remains an obstruction to fish passage because of the shallow skim of water over smooth concrete. High flows are necessary to achieve the depth at which fish could pass, at which point the water velocities over the smooth concrete are likely to become an impediment. It is understood that this problem was not tackled during the fish pass construction project because of the issue of liability for the integrity of the bridge structure if the culvert base was altered. This is a pity, because a very simple solution is possible which would pose minimal risk to the bridge structure. Low baffles bolted (or cast) onto the concrete base to concentrate and slow flows would solve the problem (see Recommendations section). Photo 1 Photo 2 Photo 3 Photo 4 Lip at the upstream end of the Denil pass and at the edge of the mass concrete. Photo 5 The bridge culvert remains a challenge for migrating fish A large number of salmonid fry were observed in the pools downstream of the fish pass. These could be the result of salmon fry stocking (Robert Rosell, pers. comm.). Bolesbrook Farm is the upstream end of DADAC fishing. The farmer here is conservation-minded and this has been recognised with awards for the way the farm is managed. This is reflected in the river upstream of the road bridge where a buffer strip between the fields and river is present along the right bank (Photo 6). As a result, a healthy riparian zone has developed with emergent vegetation (long grasses, rushes and reeds) and low, bushy sallow trees providing superb low cover over the water – excellent for holding fish. The condition of the right bank is a great example of good marginal habitat and its current state is “just right” – some light maintenance of the trees may be required (such as an annual rotational coppice of about 1 in 8 trees to maintain a mixed height and healthy understory vegetation). Unfortunately, the good margin is not complemented by the in-stream conditions because this section of river is very slow flowing and not great trout habitat. The reason for the slow flow appears to be a naturally low gradient on this section because the flow velocity has not increased despite the removal of an impoundment downstream (see below). The left bank upstream of the bridge, in contrast to the right bank, is grazed pasture and has a poor quality riparian zone (Photo 6). The banks are steep, possibly because of previous land drainage works, and there is little vegetation present other than grass. The grazed banks do however provide easy access for angling. Some temporary (electric) fencing could be utilised here to reduce grazing pressure on a marginal strip and encourage better riparian habitat; allowing grazing for short periods would keep vegetation in check and maintain angling access. At the upstream end of the Bolesbrook Farm section is the confluence of the Lagan and its tributary the Little Lagan. A sewage treatment works discharge enters the river here from a recently upgraded works. The river below the discharge appeared clean and no water quality problems have been noted here by club members. The Little Lagan has been engineered and straightened and has poor in-stream habitat (Photo 7); there are the remnants of a low weir here – maybe a previous attempt at habitat enhancement? A large fish kill occurred on the Little Lagan about 8 years ago as a result of a pollution incident from a farm; DADAC were awarded compensation which was spent on the fish pass described above. The Lagan upstream of the Little Lagan has a steeper gradient than downstream and is noted as being a prolific area for the production of juvenile trout. Land use alongside the river here was silage production and slurry spreading following the first cut was taking place (Photo 8). Downstream of Black Bog Road bridge the river occupies what appears to be an engineered channel with a trapezoidal cross-section, a large spoil bank on the left bank and the water level low in the channel (Photo 9). These appear to be the remnants of an impoundment and old mill race (behind the LHB spoil bank). The impounding weir has recently been bypassed; a meander has been cut off and the river diverted into a short section of new channel (Photo 10). This was done in order to reduce flooding of land adjacent to the now dry meander and has effectively removed the impounding effect of the weir. On the right bank of the river here (NW 35469 08014) there was a discharge to the river from a quarry. The discharge was discoloured and carrying suspended solids which were visibly affecting the watercourse for approximately 40 metres downstream (Photo 11). The input of sediment from quarry drainage and also from the washing down of roads (which sluices fine sediment into surface drains and hence the river) in the vicinity of the quarry continues to be a cause for concern to DADAC. Fine sediment clogs gravels and impacts upon the survival of trout and salmon eggs and upon invertebrate communities. Turning over stones in this area revealed olive nymphs (Baetidae), hog louse (Asellus aquaticus), shrimp (Gammarus pulex), blackfly larvae (Simulidae) and leeches. These invertebrate taxa are moderately tolerant of organic enrichment and no groups sensitive to organic pollution were observed, indicating organic enrichment of the watercourse. Photo 6 Contrast between the grazed and ungrazed banks upstream of Black Bog Road Photo 7 Little Lagan Photo 8 Land use at the Lagan / Little Lagan confluence Photo 9 Downstream of Black Bog Road. Lowered water levels following bypassing of the weir (below).